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TPS65981: Is an application mandatory?

Steve Schefter
Expert 1780 points
Part Number: TPS65981

Hi.

Can the TPS65981 be used without an application in the attached SPI flash and just control over I2C?

The Flash Read Flow in the datasheet, along with the Memory Invalid Flow show the device presenting a SWD interface on the USB-C lines for programming the flash.  Does it permanently remain in that state for programming or is it possible to change the interface to, for example, a downward facing port via register CMD1?

Thanks,
    Steve

  • 0
    TI__Genius 9630 points

    Hello,

    I've assigned this to the relevant expert who will get back to you shortly 

    Regards,

    Emma

  • 0
    TI__Genius 12700 points

    Hi Steve,

    The TPS65981 will attempt to load configurations from the SPI Flash so that you have the full capabilities of the device. If you do not use a SPI Flash, you will have very limited functionality. You can control the device via I2C using an external host, but you still won't be able to set specific configurations such as PDO's and etc. unless you load from Flash. 

    Are you seeing errors when you attempt to load from your SPI Flash? If you are flashing for the first time, you have to flash the full image binary at the beginning so that the region headers are set up correctly. As far as the SWD, yes it is waiting for these pins to be configured or VBUS to be present to sink power. I would recommend following the procedure for providing valid configurations on your SPI Flash for the PD controller to be programmed correctly.

    You can take a look at the Host Technical Reference Manual, Table 1-2 which shows all of the 4CC commands you can use to interact with the PD controller. I would also recommend reading over the Firmware User's Guide application note as well for more information on certain topics.

    Thank you,

    Hari

  • 0 in reply to Hari Patel1
    Expert 1780 points

    Hi Hari.

    Currently there is nothing programmed into the attached SPI flash, so the device will be getting into the memory invalid flow.

    When I try the 4CC commands, I'm not seeing what I expect in terms status.  For example, when I write 0x4 0x53 0x57 0x44 0x46 (len 4, SWDF) to CMD1, CMD1 reads back as though it processed the command (reads 0x4 0x0 0x0 0x0 0x0).  However, the status register reads back as all zeros so it is not indicating that the data role is DFP.

    According to Table 4-9, the data role swap is complete after the negotiation with the attached device (a phone in my case) is complete.  That, of course, can only happen if the lines of the USB-C port do not continue to present a SWF interface.

    Do the commands in fact take the USB-C lines out of SWF mode or do they remain in that mode, making them only useful for debugging/programming and not for USB-C operation?

        Steve

  • 0 in reply to Steve Schefter
    TI__Genius 12700 points

    Hi Steve,

    No just sending those commands won't take it out of SWD. This will only be presented on the SBU pins however. Is there a reason you aren't able to flash the configurations into your memory? Once flashed the PD controller will configure to those settings at power up and will be able to do the swaps hands off.

    Thank you,
    Hari

  • 0 in reply to Hari Patel1
    Expert 1780 points

    Hi Hari.

    I do not have the programming tools at my location.

    I missed that SWD just uses the SBU pins on the USB-C interface.

    However, I'm still unclear on what the chip is capable of doing without an application.  Can it operate as a DFP on D+/D- while it is in SWD mode?

    Thanks,
         Steve

  • 0 in reply to Steve Schefter
    TI__Genius 12700 points

    Hi Steve,

    I see, that may be an issue then. I thought that you might've been getting programming issues. Unfortunately, the TPS56981 device requires a valid image in flash in order to operate. If you do not provide the appropriate configurations via Flash programming then the device may not even provide a response to 4CC commands. 

    I would recommend adding the flash programming process in your design to have the full functionality of the device.

    Thank you,

    Hari

  • 0 in reply to Hari Patel1
    Expert 1780 points

    Thanks Hari.

        Steve